Reliability of the pattern hair loss classifications: a comparison of the basic and specific and Norwood-Hamilton classifications.

Pattern hair loss (PHL) is the most common form of baldness in both sexes. The Norwood-Hamilton classification is the most commonly used classification worldwide, but it has many limitations. The basic and specific (BASP) classification was introduced as an improvement over the Norwood-Hamilton classification. Previous research was done to estimate the reliability of the Norwood-Hamilton classification and the result was unsatisfactory. However, the reliability of the BASP and Norwood-Hamilton classifications has not yet been compared. Eight dermatological specialists, 17 dermatological residents and 15 general physicians classified PHL in 100 sets of photographs using both the BASP and Norwood-Hamilton classifications. Intergroup reproducibility was evaluated by examining the match rate of the individual data in each group and the match rate between hair specialist and the other examiners. Intragroup repeatability was determined by calculating the match rate between the first and second studies. In terms of intergroup reproducibility of the match rate for individual data in each group, the basic type had the best agreement, the specific type had the second best, and the Norwood-Hamilton classification had the lowest match rate. In comparison, hair specialist and intragroup repeatability showed the same patterns. The BASP classification not only distinguishes all kinds of hair loss patterns, but also has better reproducibility and repeatability than the Norwood-Hamilton classification.